Practical Problems in VLSI Physical Design TimberWolf Placement (1/16)

TimberWolf 7.0 Placement Perform TimberWolf placement

Based on the given standard cell placement Initial HPBB wirelength = 23

Practical Problems in VLSI Physical Design TimberWolf Placement (2/16)

First Swap Swap node b and e

We shift node h: on the shorter side of the receiving row

Node b included in nets {n3, n9}, and e in {n1, n7}

Practical Problems in VLSI Physical Design TimberWolf Placement (3/16)

Computing ΔW ΔW = wirelength change from swap

Practical Problems in VLSI Physical Design TimberWolf Placement (4/16)

Estimating ΔWs ΔWs = wirelength change from shifting

h is shifted and included in n4 = {d,h,i} and n7 ={c,e,f,h,n}

h is on the right boundary of n4: gradient(h)++

h is not on any boundary of n7: no further change on gradient(h)

Practical Problems in VLSI Physical Design TimberWolf Placement (5/16)

Estimating ΔWs (cont)

Practical Problems in VLSI Physical Design TimberWolf Placement (6/16)

Accuracy of ΔWs Estimation How accurate is ΔWs estimation?

Node h is included in n4 = {d,h,i} and n7 ={c,e,f,h,n}

Real change is also 1: accurate estimation

Practical Problems in VLSI Physical Design TimberWolf Placement (7/16)

Estimation Model B Based on piecewise linear graph

Shifting h causes the wirelength of n4 to increase by 1 (19 to 20) and no change on n7 (stay at 28)

Practical Problems in VLSI Physical Design TimberWolf Placement (8/16)

Second Swap Swap node m and o

We shift node d and g: on the shorter side of the receiving row

Node m included in nets {n5, n9}, and o in {n2, n10}

Practical Problems in VLSI Physical Design TimberWolf Placement (9/16)

Computing ΔW ΔW = wirelength change from swap

Practical Problems in VLSI Physical Design TimberWolf Placement (10/16)

Estimating ΔWs Cell d and g are shifted

d is included in n4 = {d,h,i}, n6 ={d,k,j}, and n8 ={d,l}

d is on the right boundary of n6 and n8

So, gradient(d) = 2

Practical Problems in VLSI Physical Design TimberWolf Placement (11/16)

Estimating ΔWs (cont) Cell d and g are shifted

g is included in n1 = {a,e,g}, and n9 ={b,g,i,m}

g is on the right boundary of n1 and n9

So, gradient(g) = 2

Practical Problems in VLSI Physical Design TimberWolf Placement (12/16)

Estimating ΔWs (cont)

Practical Problems in VLSI Physical Design TimberWolf Placement (13/16)

Third Swap Swap node k and m

We shift node c: on the shorter side of the receiving row

Node k included in nets {n3, n6 , n10}, and m in {n5, n9}

Practical Problems in VLSI Physical Design TimberWolf Placement (14/16)

Computing ΔW ΔW = wirelength change from swap

Practical Problems in VLSI Physical Design TimberWolf Placement (15/16)

Estimating ΔWs Cell c is shifted

c is included in n3 = {b,c,k,n} and n7 ={c,e,f,h,n}

c is on the left boundary of n3

So, gradient(c) = −1

Practical Problems in VLSI Physical Design TimberWolf Placement (16/16)

Estimating ΔWs (cont)